Abstract. Based on a terahertz (THz) pipe-based near-field imaging system, we demonstrate the capability of THz imaging to diagnose freshly surgically excised human colonic tissues. Through THz near-field scanning the absorbance of the colonic tissues, the acquired images can clearly distinguish cancerous tissues from healthy tissues fast and automatically without pathological hematoxylin and eosin stain diagnosis. A statistical study on 58 specimens (20 healthy tissues and 38 tissues with tumor) from 31 patients (mean age: 59 years; range: 46 to 79 years) shows that the corresponding diagnostic sensitivity and specificity on colonic tissues are both 100%. Due to its capability to perform quantitative analysis, our study indicates the potential of the THz pipe-based near-field imaging for future automation on human tumor pathological examinations. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

For overcoming the limitation of a low signal‐to‐noise ratio (SNR) in practical applications of luminescent photoelastic coating (LPC) method, a new LPC configuration applied in the LPC method is presented. Based on a brief introduction on the principle of molecular luminescence, the intensity formula for the new LPC is derived according to the theory of photoelasticity. Through the comparative analysis with the existing coating configurations (dual‐layer coating and single‐layer coating), the feasibility of this new LPC used in the LPC method for experimental strain analysis is proved theoretically, and the signal intensities of the LPC method can be increased by over two times.

Luminescent photoelastic coating (LPC) methods are used to measure the full-field shear strain and its principal direction. These methods apply a liquid LPC onto the surfaces of the structures to be measured. To correct the effects of coating thickness non-uniformity on the quantitative shear strain measurements, a non-contact method is proposed for coating thickness measurements. The proposed method establishes a linear calibration curve between the thickness and the luminescent signal intensity of the test coating. The results show that the linear calibration curve of the intensity and the thickness of the LPC can be obtained by incorporating an appropriate concentration of the luminescent dye into the photoelastic coating. The correlation coefficient of this linear calibration curve is more than 0.999.

To determine the individual values of the two strain components by separate principal strains, a theoretical model of strain separation by oblique incidence with a new luminescent photoelastic coating configuration is presented. Considering the non-strain related refraction effect included in the total optical response at oblique incidence, the small incidence angle technique for simplifying the post-processing complexity is given. To affirm the validity of this strain separation method based on small oblique angles, the signal-to-noise ratio for providing sufficient signal intensity has been theoretically analyzed.

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